412 Birds of Colorado 



from which it seems to have been recorded is between Albuquerque 

 and Mesilla on the Rio Grande in New Mexico (Brewster, "Bull. Om. 

 Club," VII., p. 147). 



Family HIRUNDINIDiE. 



Bill short, flat, very broad at the base, triangular 

 in shape when viewed from above ; edges of the mandibles 

 smooth, upper slightly notched. Gape very wide, rictal 

 bristles weak. Wings long and sharp-pointed, of nine 

 primaries only, the two outer (8th and 9th) the longest 

 and subequal to one another ; tail of twelve feathers, 

 usually more or less forked ; feet short, small and weak, 

 iU adapted for progression on the ground. Only one 

 moult in the year, in spring. Sexes usually alike and the 

 young closely resembling the adults. 



The Swallows form a well-marked and sharply isolated 

 family with no very close allies. Over a hundred species 

 are recognised, and they are distributed all over the 

 globe, except in the Arctic and Antarctic regions. 



Key of the Genera. 



A. Nostrils rounded, opening superiorly, without operculum or 



overhanging scale. 



a. Larger— wing over 5 ; tail distinctly forked. Progne, p. 413. 



b. Smaller — wing under 5 ; tail square Petrochelidon, p. 415. 



c. Smallest — wing mider 4-5 ; tail square ; outer primary roughed 



with hooks Stelgidopteryx, p. 422. 



B. Nostrils elongate or oval, opening laterally below an operculum 



or overhanging scale. 



a. Lower part of the tarsus with a tuft of feathers. 



Riparia, p. 421. 



b. No tuft of feathers on the lower part of the tarsus. 



a* Tail very strongly forked for at least ^ of its length ; 

 the outer feather attenuated ; a white spot on the 

 inner web of each tail-feather. Hirundo, p. 416. 



b^. Tail less strongly forked ; the outer feathers not attenu- 

 ated ; no white spots on the tail, 

 a' Tail longer, about ^ wing, forked for about J its length. 



Iridoprocne, p. 418. 

 b' Tail shorter, about f wing, forked for about :' its length. 



Tachycineta, p. 420. 



